FAQ
TL;DR: Ultrapure water (<0.1 µS cm-1) withstands 230 V only until contamination; “one fingerprint can raise its conductivity 1 000×” [Elektroda, serwal, post #3900425] ASTM-rated transformer oil offers ≈12 kV mm-1 dielectric strength [ABB, 2023]. Why it matters: choosing the correct liquid avoids instant shorts in DIY immersion-cooled electronics.
Quick Facts
• Dielectric strength, fresh transformer oil: 10–15 kV/mm; drops below 5 kV/mm at >0.5 % moisture [ABB 2023][NREL 2019].
• Polish retail price: 7–10 PLN / L in energy-equipment shops [Elektroda, fysiek, post #3900399]
• Ultrapure water conductivity: 0.055 µS/cm at 25 °C; tap water ≈500 µS/cm [ASTM D1125].
• Mineral-oil thermal conductivity: 0.13–0.15 W m-1 K-1 (≈20 % lower than water) [Shell TechSheet 2022].
• Typical mid-tower PC needs ≈15 L oil for full submersion [Puget Systems 2021].
Does distilled water stay non-conductive at 230 V?
No. Freshly distilled water starts near 1 MΩ cm, but airborne dust and CO₂ dissolve within minutes, creating ions that drop resistance by orders of magnitude [Elektroda, Qbuś, #3900263]. Even stainless-steel electrodes leach ions, accelerating failure [Elektroda, serwal, post #3900425]
Why does a small impurity make water conductive so fast?
Water molecules are polar. Ionic dust, acids, or metal ions complete a circuit. One sweaty fingertip adds ≈0.1 g salts—enough to push conductivity toward 1 mS cm-1, a 10 000× jump [WHO Drinking-Water Stats 2020].
What liquid insulators are proven safe for PC immersion?
- Transformer (mineral) oil—industry standard, dielectric ≥10 kV/mm [ABB 2023].
- White mineral oil—food grade, similar properties but lower sulfur.
- 3 M Novec engineered fluids—non-flammable but cost ≈€90/L [3M Datasheet 2022].
Where can I buy transformer oil and how much will it cost?
Local electrical-equipment wholesalers and online energy-supply stores stock 25-L cans. Forum users report 7 PLN / L retail in Poland [Elektroda, fysiek, post #3900399]; EU web shops list €2–€3 / L plus shipping (2024 price check).
How do I prepare transformer oil before filling the case?
- Pre-heat to 50 °C for two hours to drive off dissolved moisture.
- Filter through a 1 µm fuel filter to remove particulates.
- Test dielectric; aim ≥8 kV/mm using a handheld breakdown tester. Only then pour. [ABB Handbook 2023]
Can I just use motor oil, antifreeze, or propylene glycol?
Motor oil works short-term (see YouTube demo in thread) but oxidation darkens it and dielectric falls fast [Elektroda, woytekp, post #3901955] Antifreeze (ethylene/propylene glycol) is corrosive and moderately conductive—risk of board damage [Elektroda, tronics, post #3903910] Glycol also releases toxic vapors above 60 °C [ECHA 2022].
Will my hard drive survive submerged in oil?
Probably not. Each HDD has a barometric vent; oil seeps in and destroys the air bearing [Elektroda, woytekp, post #3910502] SSDs lack moving parts and work fine when connectors are sealed. Edge case: one user ran a laptop HDD half-dipped for two weeks before head stiction killed it [Mineral Oil PC Blog 2019].
How much cooler will components run in oil compared with air?
Expect CPU and VRM temperatures ≈10–15 °C lower under forced oil circulation at 3 L min-1, according to Puget Systems’ public bench tests (Ryzen 5 5600X) [Puget 2021]. Passive oil baths show only 3–5 °C improvement because oil’s thermal conductivity is lower than water or copper blocks.
What maintenance does an oil-cooled build require?
Change or vacuum-filter oil every 12 months; oxidation raises acid number and can corrode solder. Check dielectric quarterly; a 40 % drop signals water ingress [NREL 2019]. Replace clogged fans—they spin slower in viscous fluid.
What failure modes should I watch for?
- Moisture absorption: dielectric strength can fall below 5 kV/mm, causing arcing [NREL 2019].
- Solder mask delamination after long exposure to hot oil (observed in 8 % of boards at 18 months) [IEEE IRPS 2020].
- Fire risk: used oil’s flash point may drop under 150 °C if contaminated with fuel or solvents.
How can I measure fluid conductivity or breakdown voltage at home?
Use a handheld TDS meter (≈€15) for µS cm-1 reading; aim below 5 µS cm-1. For breakdown, hobby kits with 2 mm-gap electrodes and neon-transformer supply give pass/fail at 5 kV/mm. Always wear insulating gloves and eye protection [Fluke Safety Note 2022].
Is mineral oil the same as transformer oil for this purpose?
No. All transformer oils are mineral oils, but they meet IEC 60296, ensuring low sulfur, antioxidation additives, and moisture <35 mg kg-1. Generic mineral oil lacks those guarantees, so dielectric strength varies wildly (4–14 kV/mm measured in hobby tests) [IEC 60296 Spec 2021].
